Low entropy engine



Nov. 25, 1969 w. L. MIN-ro Low'ENTRoPY'ENGINE Fled July 6, 1967 INVENTOR Mmmm Alm/m B7 fn@ MW ATTORNEY United States Patent O M lU.S. Cl. 60--36 6 Claims ABSTRACT 0F THE DISCLOSURE A prime mover system includes a gas uid driven engine, a condenser, a pump, a boiler and a super-heater connected in a closed loop and containing as a drive medium a non-flammable fluid having a latent heat of vaporization of less than 100 gram-calories per gram at the operating temperature of the condenser, and a boiling point of less than 95 C. at atmospheric pressure, and a critical temperature at least 10 C. higher than the temperature of the condenser cooling fluid, such as the halogenated low boiling point hydrocarbons, for example, trichloromonofluoromethane. The condenser is valved to maintain a pressure therein at least equal to the condensation pressure of the drive fluid at a temperature higher than the temperature of the condenser cooling medium, and the boiler heater is automatically regulated to maintain the boiler temperature or pressure at an adjustable predetermined value. An adjustable throttle valve is located `between the engine input and the boiler.

Background of the invention The present invention relates generally to improvements in prime mover systems and it relates particularly to an improved external combustion engine system.

The conventional steam engine, as a source of motive power, possesses properties which make it superior under many conditions to other combustion engines. Whether a turbine or a reciprocating engine, it is reliable, rugged, simple and compact and has a torque versus speed characteristic which minimizes torque converter and transmission requirements. It is easy to control, regulate and ervice and is highly versatile and adaptable mechanism. Moreover, in as much as the combustion is externally effected, different types of fuels may be efficiently employed.

The steam engine as heretofore employed possesses, however, important drawbacks and inherent disadvantages which have largely limited its applications to relatively high power installations. The use of steam as the drive medium is necessarily accompanied by a low order of inherent eficiency. By reason of the high latent heat of vaporization of the water a large percentage of the overall heat input is dissipated in the condenser stage contributing to such low efficiency and requiring the use of relatively large condensers. Furthermore, as a consequence of the low molecular weight of the steam, large volumes of steam must be handled relative to the power capacity necessitating the use of large diameter conduits, a large engine and large valves. The large diameter necessitates heavier walls to achieve the hoop strength necessary to contain the pressure. Such heavier and larger construction is more costly than in the system of the present invention.

The power output of an expansion engine is a function of the pressure drop across it, Vbut to achieve high pressure differentials, steam must be heated to a relatively high temperature, necessitating the use of expensive materials of construction to achieve even modest eiciencies.

In the present invention, such high pressure dierentials are achieved with relatively low temperatures, permitting 3,479,817 Patented Nov. 25, 1969 the use of ordinary, less expensive materials of construction.

Summary of the invention It is a principal object of the present invention to provide an improved prime mover system.

Another object of the present invention is to provide an improved external combustion engine system.

Still another object of the present invention is to provide an improved expanding gas external combustion engine system possessing the advantages of a steam engine system but eliminating many of the drawbacks thereof.

A further object of the present invention is to provide an improved prime mover system of the above nature characterized by its eiciency, simplicity, ruggedness, compactness, reliability and adaptability, and the minimization of thermal pollution of ambient air or water.

The above and other objects of the present invention will become apparent from a reading of the following description taken in conjunction with the accompanying drawing which illustrates a preferred embodiment thereof.

In a sense the present invention contemplates the provision of a prime mover system comprising a gas tiuid driven engine, a boiler containing a drive medium having a latent heat of vaporization of less than 100 gram calories per gram and a boiling point less than 95 C. at atmospheric pressure, a super-heater to further increase the enthalpy of the vapor, condenser exposed to a cooling medium connected to the outlet of said engine for liquifying the outlet gasses from said engine, said drive medium having a critical temperature higher than the temperature of said condenser cooling medium, means for injecting liquid drive medium from said condenser into said boiler, and means including an adjustable power or speed control valve connecting the outlet of said boiler to the inlet of said engine.

The engine is preferably a turbine although an expandible chamber type of engine, such as the conventional reciprocating piston engine, may be employed. The boiler heater unit is advantageously of the flash boiler type with its output connected to the engine input by way of a super-heater and throttle valve for controlling the engine power. The condenser may be any conventional heat exchange unit in which the cooling medium may be `circulated air or other gas or liquid and means are advantageously provided for maintaining the condenser under pressure whereby to increase the condensation tempera ture of the drive medium circulating through the condenser and increase the capacity of the condenser by reason of the minimum required liquitication temperature. The injection means is advantageously a pressure pump which may -be driven by the engine. A mechanism is provided for automatically regulating the boiler heater to maintain an adjustable substantially constant temperature or pressure in the boiler. Examples of drive mediums which may be employed to great advantage are the halogenated hydrocarbons, for example, trichloromonotluoromethane, dichlorodifluoromethane, chlorodiuoromethane, dichlorotetrafluoroethane, carbon tetrachloride, trichlorotrilluoroethane, or mixtures thereof.

The improved prime mover system possesses the advantages of a steam engine without its drawbacks. It is of much greater efficiency, employs a smaller and more cornpact engine, as well as lighter and smaller piping, boiler,

Brief description of the drawing The drawing is a schematic diagram of a prime mover system embodying the present invent1on.

Description of the preferred embodiment Referring now to the drawing which illustrates a preferred embodiment of the present invention, the reference numeral generally designates the improved prime mover system in which the individual components are of well known construction and operation and are accordingly diagrammatically illustrated. The system, 10 is in the form of a closed drive fluid loop and includes a boiler 11 preferably a ash boiler, including a fuel burner 12 conneccted to a suitable fuel source and controlled by an electrically energized assembly 13. The burner 12 is controlled in the known manner to maintain the pressure or temperature or both in the boiler 11 at an adjustable constant level by means of a pressure or temperature sensing element 14 positioned in the boiler and connected by an adjustable regulator network 16 to the control assembly 13.

The outlet of the boiler 11 is connected to the super heater 15, thence through an adjustable valve or throttle 17 to the input port of a turbine 18 generally of the steam type but proportioned to the characteristics of the drive vapor. The throttle valve 17 functions to adjust the ow of gaseous drive uid from the super-heater to the turbine 18 and hence control the turbine power output. It should be noted that a conventional type expansible chamber engine, may be substituted for the turbine 18. The outlet port of the turbine 18 or the expansible chamber engine as the case may be, is connected through an optional first check valve 19 to a forced air cooled condenser 20, the outlet of the condenser 20 being connected through a second check valve 21 to the input of a liquid pump injector 22 driven by a take-off from the turbine 18 or by a separate variable motor 23. The outlet of the pump 22 is connected to the input of the boiler 11. The drive shaft of the turbine 18 is connected either directly or through a suitable transmission to a device 24 which is to be motivated, for example, an electrical generator, pump, compressor or the like. Where the drive speed of the device 24 is important, the throttle valve 17 may be automatically regulated in response to variations in such speed, in the known manner to maintain an ad- `justable constant speed. An auxiliary generator 26 may likewise be driven by the turbine 18 and its output employed to energize the throttle valve 17, the control assembly 13 and the pump drive motor 23, or any one or combination thereof.

The drive uid employed in the above described system is trichloromonofluoromethane, it being understood that other drive uids meeting the requirements earlier set forth may be employed.

As a specific example of the operation of the present prime mover system the drive iluid was trichloromonouoromethane, the condenser check valve is adjusted to a condenser pressure of p.s.i.a. and the regulator 16 is adjusted to a boiler pressure of 400 p.s.i.a. The vapor temperature leaving the boiler 11 is about 167 C. and 222 C. leaving the super-heater, under full load running conditions of the turbine 18 the eiuent exhaust vapor has a temperature of about 65 C. The condenser 20 is air cooled and the outlet condensed liquid has a temperature of about 55 C., the heat losses in the condenser 20 being about 74.5 B.t.u. per pound of drive medium. Under the above conditions the overall elliciency of the drive fluid loop, that is the percentage of the input energy delivered by the uid to the turbine 18 is about 32%. This compares to a comparable steam system efliciency of 10% for thte same temperature dilferentials and super-heat, wherein the latent heat of vaporization loss in the condenser amounts to approximately 1000 B.t.u. per pound of steam.

While there have been described and illustrated preferred embodiments of the present invention, it is apparent that numerous alterations, omissions and additions may be made without departing from the spirit thereof.

What is claimed is:

1. A prime mover system comprising a closed sealed circuit containing a drive medium having a latent heat of vaporization of less than 100 gram calories per gram and a boiling point less than C. at atmospheric pressure, said closed sealed circuit including boiler means (11,15) for heating and vaporizing said drive medium, a vapor engine (18), having an input and output, means including a control throttle (17) for connecting said boiler means to said vapor engine input, means including a condenser (20) exposed to a cooling medium and having an input connected to the output of said engine and an output for liquifying the outlet gasses from said engine, means (21) for maintaining the internal pressure of said condenser at greater than atmospheric and means (22,23) for injecting said liquid drive medium from said condenser output into said boiler means, said drive medium being non-inflammable and having a critical temperature higher than the temperature of said cooling medium.

2. The prime mover of claim 1 wherein said critical temperature of said gas medium is at least 10 C higher than said condenser cooling medium temperature.

3. The prime mover of claim 1 said drive medium having a boiling point at said condenser internal pressure at least 10 C. greater than ambient atmospheric tempera ture.

4. The prime mover of claim 1 wherein said drive medium has a molecular weight of at least 40.

5. The prime mover of claim 1 wherein said drive medium has a latent heat of vaporization of 5 to 100 gram calories per gram, a boiling point of 180 C. to +95 C. at atmospheric pressure, and a molecular weight between 40 and 200.

6. The prime mover of claim 1 wherein said drive medium is selected from the class consisting of trichloromonouoroethane, dichlorodifluoromethane, chlorodiuoromethane, dichlorotetrauorethane, carbon tetrachloride, trichlorotriuoroethane, or mixtures thereof.

References Cited UNITED STATES PATENTS 1,957,893 5/1934 Lloyd 60-36 2,301,404 11/1942 Holmes 60-36 3,216,199 ll/1965 Shaw et al. 60-l07 MARTIN P. scHwADRoN, Primary Examiner R. R. BUNEVICH, Assistant Examiner U.S. Cl. X.R. 60-95 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.. 3 479 817 Dated November 25, 1969 Inventor(s) WALLACE L. MINTO It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

column 4, line 6, "327," should read 22%; and claim 6, lines 2 3, "trichloromonofluoroethane" should read trichloromonoflporomethane-.

Signed and sealed this 1 7th day of August 1 971 (SEAL) Attest:

EDWARD M.FLETCHER,JR. WILLIAM E. SCHU'YLER, JR. Attestng Officer' Commissioner of Patents F ORM P04050 (1 O-69l 

